1. Field of the Invention
The present invention relates generally to digital projectors with one or more color settings. More particularly, the invention relates to a system for monitoring the color settings in such a digital projector.
2. Related Art
One type of digital light processor or DLP in common use today employs a digital micromirror device (DMD) to selectively reflect light to produce an image. The light is provided by a high intensity projector light source, and is reflected off of an array of perhaps millions of microscopic mirrors on a DMD chip. This chip is a micromechanical device that selectively tilts the mirrors to reflect the light in a desired pattern. The pattern is dictated by an electronic video signal, such that the entire chip can selectively reflect light to produce a video image.
Where color images are desired using a single DMD device, the light source is filtered through a rotating color wheel before striking the DMD chip. The color wheel includes red, green, and blue filters, and rotates in sync with the refresh rate of the video signal to sequentially provide red, green, and blue light for reflection. The mirrors on the DMD chip tilt as needed to reflect the appropriate quantity of each color of light to produce the desired color at a given pixel location. Upon observation, the human eye and brain blend the rapidly alternating constituent colors to perceive a full color image.
Some DLP devices include more than one color wheel, and a mechanism to switch between the two. In addition to the standard three-color (red, green, blue) wheel, these projectors can include a second color wheel with a clear or transparent segment in addition to the red, green and blue segments. The use of this second color wheel provides a brighter image because the transparent segment allows more light through the color wheel per unit time. However, because the additional light is white, the effect is to wash out the image slightly. Operation of a DLP using the first color wheel is sometimes referred to as “video” mode, while use of the second color wheel is sometimes referred to as “business graphics” mode. Operation in video mode provides excellent color saturation, but not as bright a picture. Operation in business graphics mode provides a brighter picture, but with less than ideal colors.
Some projectors with two color wheels also have a third setting, wherein neither of the color wheels are used. This setting does not filter the projected light, and thereby creates a very bright black-and-white image. Users are thus able to switch between video mode, business graphics mode, and black-and-white mode whenever desired.
The trade-off between rich color and brightness is considered appropriate in certain circumstances. For example, a video image with very rich color is generally desired for television, video, and movies. Because such viewing is frequently done in a slightly darkened room, an image of lesser brightness can be acceptable. However, in a brighter room, a brighter image is needed. This is frequently the case in places such as conference rooms, business offices, etc. where displays of text, lower quality graphics, and the like are common. Because high quality video images may not be required in such situations, a bright image without the richer color is acceptable.
While many DLP devices include the apparatus for projecting in the various illumination and color modes mentioned above, they do not typically include any mechanism for monitoring how long the projector is used in any one mode, or how often the color wheel and light intensity modes are switched. Consequently, designers and makers of DLP devices have relatively limited knowledge of which modes are most commonly used, and which projector devices are typically used in which ways. Their knowledge is largely based on speculation and conjecture, and not factual data. Thus, a projector device intended primarily for business graphics may end up more often used for high quality color video projection. Likewise, another model expected to be used more for home video projection may become popular with professionals and used frequently in a business setting where lower quality color is acceptable.